U.S. patent number 3,928,519 [Application Number 05/382,347] was granted by the patent office on 1975-12-23 for method for forming on an elongated core member a covering of thermoplastic material by extrusion.
This patent grant is currently assigned to The Furukawa Electric Co., Ltd.. Invention is credited to Hiroshi Kashiyama, Susumu Tobita.
United States Patent |
3,928,519 |
Kashiyama , et al. |
December 23, 1975 |
Method for forming on an elongated core member a covering of
thermoplastic material by extrusion
Abstract
This invention relates to a method for forming on an outer
periphery of an elongated core member, a covering layer of
thermoplastic material by extrusion, said covering layer including
outwardly and diametrically extending enlarged portions thereon
equally spaced from each other along the longitudinal axis of said
covering, comprising the step of feeding said core member at a
periodically varied velocity thereof through an extruder having a
substantially constant volumetric flow of said thermoplastic
material. Furthermore, this invention relates to a method for
producing an insulated core member for a coaxial cable comprising
the step of extruding on an elongated inner conductor an insulation
of thermoplastic material with an enlarged portion and a reduced
portion alternately provided thereon. Furthermore, this invention
relates to a method for producing an electric wire free from growth
of snow collecting thereon, said electric wire comprising a
covering layer formed thereon by extrusion, said covering layer
provided with longitudinal rib or ribs and a plurality of
peripheral ribs spaced from each other along the longitudinal axis
of said electric wire.
Inventors: |
Kashiyama; Hiroshi (Ichihara,
JA), Tobita; Susumu (Ichihara, JA) |
Assignee: |
The Furukawa Electric Co., Ltd.
(Tokyo, JA)
|
Family
ID: |
27456245 |
Appl.
No.: |
05/382,347 |
Filed: |
July 25, 1973 |
Foreign Application Priority Data
|
|
|
|
|
Jul 29, 1972 [JA] |
|
|
47-75552 |
Feb 7, 1973 [JA] |
|
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48-14622 |
Apr 4, 1973 [JA] |
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48-37850 |
Feb 14, 1973 [JA] |
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48-18708 |
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Current U.S.
Class: |
264/40.7; 72/261;
156/47; 174/28; 174/106R; 264/167; 428/399; 72/271; 156/51;
174/105R; 174/110R; 174/211; 428/379; 264/171.16; 264/171.2;
29/825 |
Current CPC
Class: |
B29C
48/325 (20190201); B29C 48/15 (20190201); H01B
13/202 (20130101); B29C 48/13 (20190201); H01B
13/18 (20130101); H01B 13/067 (20130101); B29C
48/06 (20190201); H01B 13/14 (20130101); Y10T
428/294 (20150115); Y10T 29/49117 (20150115); B29C
48/07 (20190201); B29C 48/05 (20190201); Y10T
428/2976 (20150115) |
Current International
Class: |
B29C
47/02 (20060101); B29C 47/22 (20060101); H01B
13/06 (20060101); H01B 13/20 (20060101); H01B
13/14 (20060101); H01B 13/18 (20060101); B29F
003/10 (); D01D 013/06 () |
Field of
Search: |
;173/244,109,106,107
;425/114,113,132 ;264/167,174,96,40,177R ;29/624 ;156/47.51
;161/179 ;174/105-107 ;428/379,399 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Woo; Jay H.
Attorney, Agent or Firm: Woodling, Krost, Granger &
Rust
Claims
What is claimed is:
1. A method for forming on an elongated core member a covering of
thermoplastic material with the outer diameter thereof varied along
the longitudinal axis of said core member, comprising the step of
extruding said thermoplastic material on said core member through
an extruder die while said core member is fed at a pulsatingly
varied velocity of said core member, characterized by that said
core member has a substantially constant average feeding velocity
while said thermoplastic material has a substantially constant
average volumetric flow rate at which said thermoplastic material
is extruded from said extruder die; and that said pulsatingly
varied velocity of said core member is established at a point
before entry of said core member into said extruder to have a
maximum value which is greater than the average flow rate of said
thermoplastic material through said extruder die at the outlet
thereof and to have a minimum value which is negative, with said
maximum and minimum values alternately repeated in a periodical
manner whereby said covering varies in the outer diameter thereof
along the longitudinal axis of said core member.
2. A method as set forth in claim 1, wherein said pulsatingly
varied velocity of said core member is further established at a
point after cooling and solidification of said covering on said
core member in synchronism with the pulsatingly varied velocity of
said core member at the point before entry into said extruder.
3. A method as set forth in claim 1, wherein said extruder die
outlet includes a recess provided in said outlet at the front
thereof and further comprising the step of controlling the
configuration in said covering applied on said core member when
said core member is fed at a lower velocity than said average flow
rate of said thermoplasitc material through said die at the outlet
thereof.
4. A method as set forth in claim 3, wherein said recess in said
die outlet is cooled at the wall thereof.
5. A method for producing an insulated core for a coaxial cable,
said insulated core including an elongated inner conductor and an
insulation having large and small diameter portions alternately and
continuously provided on said inner conductor, comprising the step
of extruding thermoplastic insulation on said inner conductor
through an extruder die while said inner conductor is fed at a
pulsatingly varied velocity of said inner conductor, characterized
by that said inner conductor has a substantially constant average
feeding velocity while said thermoplastic insulation has a
substantially constant average volumetric flow rate at which said
thermoplastic insulation is extruded from said extruder die; and
that said pulsatingly varied velocity of said inner conductor is
established at a point before entry of said inner conductor into
said extruder to have a maximum value which is greater than the
average flow rate of said thermoplastic insulation through said
extruder die at the outlet thereof and to have a minimum value
which is negative, with said maximum and minimum values alternately
repeated in a periodical manner.
6. A method for producing a coaxial cable comprising the steps of
rolling up a strip of conducting material over the insulated core
formed in accordance with said claim 5 so that the opposite
longitudinal edges of said strip abut with each other, welding said
abutting edges of said strip into a resultant cylindrical outer
conductor, drawing said outer conductor through a die to closely
engage said conductor at the inner surface thereof with the large
diameter portions of the insulator on the inner conductor of said
insulated core and heating said cylindrical outer conductor to
thermally bond said outer conductor at the inner surface thereof to
said large diameter portions of said insulator.
7. A method for producing an electric wire to inhibit growth of
snow thereon, said electric wire including a core conductor and an
insulation including a plurality of peripheral ribs spaced
longitudinally from each other and at least one longitudinal rib,
both of which are provided on said core conductor, comprising the
step of extruding thermoplastic insulation on said core conductor
through an extruder die while said core conductor is fed at a
pulsatingly varied velocity of said core conductor, said extruder
die including a longitudinal groove to form said longitudinal rib,
characterized by that said core conductor has a substantially
constant average feeding velocity while said thermoplastic
insulation has a substantially constant average volumetric flow
rate at which said thermoplastic insulation is extruded from said
extruder die; and that said pulsatingly varied velocity of said
core conductor is established at a point before entry of said core
conductor into said extruder to have a maximum value which is
greated than the average flow rate of said thermoplastic insulation
through said extruder die at the outlet thereof and to have a
minimum value which is negative, with said maximum and minimum
values alternately repeated in a periodical manner whereby said
peripheral ribs are formed on said core conductor.
Description
FIELD OF THE INVENTION
This invention generally pertains to a method and an apparatus for
extruding a covering layer of thermoplastic material on an
elongated core member which may be in the form of wire, strip and
the like, such as an electric conductor, a communicating cable
core, rope, strand or the likes, and more particularly to a method
and an apparatus for extruding on an elongated core member a
covering layer with an outwardly and diametrically extending
portions provided longitudinally in a properly spaced relation to
each other.
BACKGROUND OF THE INVENTION
In various fields, a covering of thermoplastic material is required
to be provided on an elongated core member in the form of wire,
strip or the like and in such cases to include a plurality of
peripheral enlarged portions provided in a longitudinally and
equally spaced relation to each other. In the manufacture of power
distribution cables, for example, in order to prevent snow on a
cable from growing into an enlarged lump due to its displacement
along the axis thereof, there are provided a plurality of
peripheral enlarged portions or rings longitudinally spaced from
each other. In the field of fishing net manufacture, there is
required an edge rope with a plurality of peripheral ribs provided
thereon and longitudinally spaced from each other whereby the ribs
on the rope can prevent threads latched on the rope from displacing
along the longitudinal axis of the rope.
In one of some fields, such peripheral enlarged portions on the
elongated core member have been provided by forcing inwardly and
diametrically or squeezing the covering on the core member in a
longitudinally spaced manner after its extrusion and prior to its
cooling and solidification. However, the disadvantage of such
process is that it does not permit the feeding of the core member
at a higher speed through an extruder. In another field, the
enlarged portions on the extruded covering have been formed by
cutting the covering circumferentially so as to reduce its outer
diameter in a longitudinally spaced manner, but it advantageously
requires substantial time for cutting. The procedure has been
commonly used in which a length of tape is wound around the
extruded covering on the core member in a uniform thickness.
However, this procedure requires the step of cutting an elongated
tape into the predetermined lengths, which will be manually
operated or effected by a complicate installation with the result
that the products will become expensive.
In various fields, such as manufactures of ski sticks or fishing
rods are used non-slippery handle grips, with uneven surfaces
conventionally formed by injection because it cannot be extruded.
If a covering with a plurality of annular projections spaced
longitudinally from each other will be able to be extruded on a
core member in the form of a tubular base of a handle grip, a
plurality of handle grips will be produced by cutting the elongated
tubular base with the extruded covering into predetermined
lengths.
Furthermore, it will be mostly intended by the inventors that in
field of the manufacture of a coaxial cable for communication, an
insulation of any type is provided around an inner conductor of the
coaxial cable to space it from an outer conductor thereof. By way
of example, there is commonly used a coaxial cable, the inner
conductor of which has a plurality of insulating disks spaced
longitudinally from each other. However, mounting the disks on the
inner conductor is considerably troublesome, poor in efficiency and
unsuitable for mass production by continuous operation. The
conventional coaxial cable which comprises the insulating disks on
the inner conductor has some disadvantages one of which is that in
case the outer conductor is compressed by external force, it
contacts with the inner conductor due to its exposure causing
short-circuit. Another disadvantage is that in case water enters
the cable through the outer conductor it will unpreferably pass
along the longitudinal axis of the cable between the outer
conductor and the outer edges of the disks on the inner conductor
to cause insulation resistance to be reduced between the outer and
inner conductors over the substantial length thereof. Therefore,
the inner conductor is desired to have an insulating covering layer
over the entire length thereof and on the other hand it is required
to have a vacant space free of solid insulation while a spaced
relation can be maintained between the outer and inner conductors
because the cable is required to have an equivalent specific
dielectric constant as lower as possible. Thus, it is desirable
that the coaxial cable may have a thin insulating covering layer
over the entire length thereof with a plurality of longitudinally
spaced annular projections or disks provided on the covering layer.
But, with the prior art extruding process it is impossible to make
such covering layer with the above-mentioned disks.
OBJECT OF THE INVENTION
Accordingly, it is a principal object of the present invention to
provide a method for extruding on an elongated core member of any
cross section a covering of thermoplastic material with a plurality
of largely diametered projections spaced longitudinally from each
other.
It is another object of the present invention to provide a method
for extruding a covering of thermoplastic material with a plurality
of projections on an elongated core member, with the configuration
of the projections and their precision upon manufacturing adapted
to be controlled as desired.
It is further object of the present invention to provide an
apparatus adapted to practise a method for extruding the
afore-mentioned covering on an elongated core member.
It is further object of the present invention to provide a method
for producing an insulated core for a coaxial cable by means of
application of the method described in the first-mentioned
object.
It is another object of the present invention to provide a method
for producing an electric wire free from growth of snow thereon by
means of application of the method described in the first-mentioned
object.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, there is
provided a method for forming on an elongated core member a
covering of thermoplastic material with the outer diameter thereof
varied longitudinally, comprising the steps of extruding said
thermoplastic material on said core member through an extruder, at
constant volumetric flow rate of said thermoplastic material and
feeding said core member through said extruder with its feeding
velocity pulsatingly varied.
In accordance with another aspect of the present invention, there
is provided an apparatus for extruding on an elongated core member
a covering of thermoplastic material with the outer diameter
longitudinally varied, comprising supply means to supply said
elongated core member in a continuous manner, an extruder to
extrude said thermoplastic material on said core member
therethrough at a constant volumetric flow rate of said
thermoplastic material and means to feed said core member through
said extruder adjacent to the die thereof at pulsatingly varied
feeding velocities of said core member, said feeding means
including a constant feeder to feed said core member from said
supply means at a constant velocity of said core member and a
modulator to modulate the feeding velocity of said core member from
said feeder whereby said covering will be formed on said core
member with the outer diameter of said covering varied along the
longitudinal axis thereof.
In accordance with another aspect of the present invention, there
is provided a method for producing an insulated core for a coaxial
cable, said insulated core including an elongated inner conductor
and a thin insulating covering of thermoplastic material with a
plurality of enlarged portions spaced longitudinally from each
other, comprising the step of passing said inner conductor at a
feeding velocity thereof periodically varied through an extruder
die having a constant volumetric flow rate of said thermoplastic
material therethrough, said feeding velocity of said inner
conductor having maximum value more than the average flow rate of
said thermoplastic material through said extruder die and having
minimum value which is negative.
In accordance with another aspect of the present invention, there
is provided a method for producing an electric wire free from
growth of snow collecting thereon, said wire comprising a core
conductor and an insulator of thermoplastic material provided on
said core conductor, including a plurality of peripheral ribs
spaced longitudinally from each other and longitudinal rib means,
comprising the step of passing said core conductor at periodically
varied feeding velocities through an extruder die having a constant
volumetric flow rate of said thermoplastic material, said extruder
die having longitudinal groove means in the inner periphery of the
die adjacent to the outlet thereof to thereby form said
longitudinal rib means.
BRIEF DESCRIPTION OF THE DRAWINGS
The above-mentioned and other objects and features of the present
invention will become apparent to those skilled in the art from the
following description of some preferred embodiments with reference
to the accompanying drawings;
FIG. 1 is a schematic diagram of a system for extruding
thermoplastic material on an elongated core member in accordance
with the principle of the present invention;
FIGS. 2, 4, 6 and 8 are graphs illustrating different
characteristics respectively, in which feeding velocity of the
elongated core member through an extruder die varies with time;
FIGS. 3, 5, 7 and 9 are enlarged side views of the elongated core
members covered with thermoplastic material in use of
characteristics shown in FIGS. 2, 4, 6 and 8, respectively;
FIG. 10 is a side elevational view of one embodiment of pulsatingly
feeding means in the system illustrated in FIG. 1;
FIG. 11 is a top view of feeding means taken along line 11--11 of
FIG. 10;
FIG. 12 is a top view of portion above that as shown in FIG.
11;
FIG. 13 is an enlarged and horizontally sectional view of a guide
assembly for an oscillating roller incorporated in the apparatus as
shown in FIG. 10;
FIG. 14 is a schematic diagram of a system including an alternative
embodiment of the pulsatingly feeding means;
FIG. 15 is a fragmentary and vertically sectional view of a die in
an extruder adapted to be employed in the present invention;
FIG. 16A is an enlarged and vertically sectional view of a portion
of the die as shown in FIG. 15;
FIG. 16B is a front view of the outlet of the die as shown in FIG.
16A;
FIG. 17A is an enlarged side elevational view of an elongated core
member having a covering extruded through the die as shown in FIG.
16A, with the covering illustrated in vertical section;
FIG. 17B is a cross-sectional view of the elongated member shown in
FIG. 17A taken along line 17B--17B of FIG. 17A;
FIG. 18 is similar to FIG. 16A, but illustrating an alternative
die;
FIG. 19 is an enlarged side elevational view of an elongated core
member having a covering extruded through the die as shown in FIG.
18, with the covering illustrated in vertical section;
FIG. 20 is substantially similar to FIGS. 16A and 18, but
illustrating a modified die of an extruder;
FIG. 21 is an enlarged side elevational view of an elongated core
member having a covering extruded through the die as shown in FIG.
20, with the covering in vertical section;
FIG. 22 is an enlarged and vertically sectional view of a further
modified extruder die;
FIG. 23A is an enlarged and vertically sectional view of a further
modified extruder die;
FIG. 23B is a front view of the die shown in FIG. 23A;
FIG. 24 is a fragmentary and enlarged view of a coaxial cable
having an inner conductor covered with an insulation extruded in
accordance with the present invention;
FIG. 25A is a cross sectional view of the coaxial cable of FIG. 24
taken in line 25A--25A of FIG. 24;
FIG. 25B is a cross sectional view of the coaxial cable of FIG. 24
taken in line 25B--25B of FIG. 24;
FIG. 26 is a schematic diagram illustrating a strip of an outer
conductor formed into a cylinder around an inner conductor covered
with an insulation for manufacture of a coaxial cable and further
illustrating the tubular outer conductor reduced in diameter and
thermally bonded to the outer edges of the insulator on the inner
conductor, with portions in vertical section for purpose of its
illustration;
FIG. 27 is an enlarged front view of an extruder die employed for
manufacturing an electric wire free from growth of snow collecting
thereon;
and FIG. 28 is a fragmentary perspective view of an insulated core
of the electric wire with an insulator extruded through the die as
shown in FIG. 27.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to FIG. 1, a system embodying the principle of the
present invention is indicated generally at numeral 1 and in this
system wire member 2, one example of an elongated core member is
drawn out of a supply source 3 in which coiled wire member is
contained and fed through pulsatingly feeding means 4 into an
extruder 5 wherein a covering 6 is extruded on the wire member 2 to
provide a covered wire member 2' which in turn passes through a
cooling trough 7 for its solidification and then is wound by a
coiler 8. Pulsatingly feeding means 4, as described hereinafter,
includes a constant feeder to feed the wire member 2 from the
supply source 3 at a constant feeding velocity thereof and a
modulator to modulate the feeding velocity of that portion of the
wire member which passes through a die 5a of the extruder 5 to
provide a pulsatingly varied feeding velocity of the wire member
2.
Generally, in an extruder having a conventional cross head, such as
an extruder for covering a conductor of an electric cable,
provision of higher pressure of melted material by a driven screw
within the cross head causes a volumetric flow rate of the melted
material to become substantially constant even though covering rate
of the wire member, that is feeding velocity of the wire member
through the extruder would vary. This fact has been assured by some
tests in connection with this respect. With such volumetric flow
rate of melted material maintained at constant value, an amount of
plastic material attached to the wire member varies with the
feeding velocity of the wire member through the extruder and as a
result when the feeding velocity of the wire member is relatively
higher, an amount of attached material to the wire member per unit
cross sectional area thereof is smaller enough to apply a
relatively thinner covering 6 on the wire member while an amount of
attached material per unit cross sectional area is greater enough
to apply a relatively thicker covering to the wire member when the
feeding velocity of the same is relatively smaller. Thus, the
periodically varied feeding velocity of the wire member 2 through
the extruder 5 by the modulator of pulsatingly feeding means 4
causes the thickness of the covering 6 on the wire member to vary
along the longitudinal axis thereof to provide a corrugated outer
surface of the covering 6 which as a result has the outer diameter
varied along the longitudinal axis thereof.
It should be noted that it is important for effectiveness in varied
outer diameters of the covering 6 to consider the average flow rate
of thermoplastic material in the die of the extruder adjacent to
the outlet thereof relative to the feeding velocity of the wire
member through the extruder. More particularly, the pulsating
variation in the feeding velocity of the wire member 2 may be
effected by alternately repeating the feeding velocities of the
wire member greater and less than the average flow rate of
thermoplastic material through the die adjacent to the outlet
thereof. Thermoplastic material through the die has first flow
portion adjacent to the inner periphery of the die, second flow
portion adjacent to the wire member and third flow portion between
the first and second flow portions, all of which have different
flow rates thereof, respectively. Accordingly, "the average flow
rate of thermoplastic material through the die adjacent to the
outlet thereof" is referred hereinafter to the average value of the
flow rates of all the flow portions through the cross section of
the die outlet. The average flow rate can be determined by the
cross sectional area of the die outlet of the extruder and the
volumetric flow rate of thermoplastic material therethrough.
It will be understood that variation in the outer diameter of the
covering 6 along the longitudinal axis thereof depends upon
parameters, such as the average feeding velocity of the wire
member, wave form of the velocity, the maximum and minimum
velocities, variation pitch of the velocity (cycle) etc., which are
determined by the particular pulsatingly feeding means.
FIG. 2 shows one of the characteristics in which the feeding
velocity of the wire member v varies with time t and the
characteristic shown in this figure is generally in the form of
sine wave wherein its amplitude is smaller and variation pitch or
cycle is larger. It will be found that the minimum feeding velocity
is positive. FIG. 3 illustrates the covering 6 of thermoplastic
material applied on the wire member 2 in accordance with the
characteristic as shown in FIG. 2. It will be found that the
covering 6 has moderate variation in its outer diameter and
therefore, the wire member 2 has nodular portions 6a of the
covering spaced along the longitudinal axis thereof from each
other.
FIG. 4 shows another characteristic of the feeding velocity of the
wire member v relative to time t, which is also generally in the
form of sine wave, but somewhat larger in its amplitude than that
of FIG. 2 and shown to have the minimum feeding velocity of zero.
FIG. 5 illustrates the covering 6 of thermoplastic material applied
on the wire member 2 in accordance with the characteristic as shown
in FIG. 4. It will be found that the covering 6 of FIG. 5 has
relatively larger variation in the outer diameter of nodular
portions 6a which are formed at the moment at which the wire member
2 temporally stops to be fed.
FIG. 6 shows another characteristic of the feeding velocity of the
wire member v relative to time t, which is also generally in the
form of sine wave, but somewhat larger in its amplitude and smaller
in its variation pitch than that of FIG. 2. It should be noted that
it has the negative minimum velocity of the wire member. Thus, the
wire member 2 results to repeat relatively larger forward movement
and relatively smaller backward movement within the die of the
extruder. FIG. 7 illustrates in configuration the covering 6 of
thermoplastic material applied on the wire member 2 in accordance
with the characteristic as shown in FIG. 6. It will be noted that
the covering of FIG. 7 has acute variation in diametrically
enlarged portions 6a because of thermoplastic material on the wire
member 2 stopping at the front of the die 5a due to the wire
member's backward movement. Thus, it will be appreciated that if
there occurs such backward movement of the wire member 2, then the
front configuration of the die 5a may determine that of the
diametrically enlarged portions 6a of the covering 6 on the wire
member, which will be hereinafter described in more detail with
reference to FIGS. 15 through 23.
The characteristic of the feeding velocity of the wire member v
relative to time t, as shown in FIG. 8 is in the form of square
wave and has the negative minimum feeding velocity of the wire
member which means that the wire member 2 will make backward
movement during a period of time. FIG. 9 illustrates in
configuration the covering 6 extruded on the wire member 2 in
accordance with the characteristic shown in FIG. 8. It will be
noted that the covering of FIG. 9 has vertically raised variation
in diametrically enlarged portions 6a because of acute variation in
the feeding velocity of the wire member 2 and that diametrically
reduced portions 6b of the covering 6 are thinner because of the
maximum feeding velocity of the wire member considerably greater
than those of FIGS. 2, 4 and 6.
As described hereinabove, the elongated core member to be covered
with thermoplastic material may be of any cross section, such as
wire, strip, tube and the likes. It may be a body with a
longitudinal rib or ribs provided thereon so as to hold the
covering on the core member from peripheral displacement relative
to one another. Alternatively, it may be provided with properly
spaced projections or indentations to prevent the covering on the
core member from longitudinal displacement relative to the latter.
Such projections or indentations may be made by embossing or
pressing portions of tubular core member, for example. Strands,
ropes, fibres and the likes have cross section varied along the
longitudinal axis thereof, which can apply the present invention
thereto. It will be understood that the aforesaid core members
should be of sufficient resistance to withstand the melting point
of thermoplastic material when it is extruded on them. Material of
the core member is dependent upon material of the covering and vice
versa. Thermoplastic material used as covering may include organic
material, such as polymer, for example, inorganic material such as
glass, for example and metallic material. The cross section of the
covering, which may be circular, elliptical, rectangular and of any
other type, may depend upon the cross section of the core member,
but it may be preferably controlled by the cross section of the
extruder die 5a, as above-described and described hereinafter in
more detail.
Referring now to FIGS. 10 to 13, there is shown an embodiment of
pulsatingly feeding means 4 for the wire member suitable for
practising the method in accordance with the present invention,
which means is illustrated to comprise a frame assembly 9
constructed of shape steels, on which a constant feeder section 10
and a modulator section 11 are mounted.
The feeder section 10 may comprise a metallic pulley 12 securedly
mounted on a shaft 13 which is in turn journalled on a base 14 by
any conventional means. The feeder section also comprises an
endless rubber belt 15 frictionally engaging the pulley 12 at the
substantially half portion thereof, which belt is shown to engage
and pass around three pulleys 16 which are in turn journalled on
the base 14 by means of respective shafts 17.
An electric motor 18 may be mounted on the base portion 9a of the
frame assembly 9, which motor has a pulley 19 secured to the output
shaft 18a thereof. On the base portion 9a is mounted a first
reduction gear 20 including on one of the sides thereof an input
shaft 21 having a duplex grooved pulley 22 secured thereto and on
the other side thereof an output shaft 23 having a sprocket 24
secured thereto. An endless belt 25 is wound between the pulley 19
on the motor output shaft 18a and the pulley 22 on the reduction
gear input shaft 21 at one of the grooves 22a thereof and
therefore, the reduction gear 20 may be driven by the motor 18. On
the shaft 13 having the pulley 12 secured thereto is mounted in the
common vertical plane to the pulley 24 a sprocket 26 which is not
shown in FIG. 10 to be operatively associated with the pulley 12
for clarification of the illustration. An endless chain 27 engages
sprockets 24 and 26 therebetween and it will be appreciated that
the pulley 12 of the feeder section 10 can be driven by the output
of the first reduction gear 20.
Since the wire member 2 from the supply source 3 shown in FIG. 1
passes through the feeder section 10 with the wire member forcedly
held between the pulley 12 and the endless rubber belt 15, the wire
member results to be fed at constant velocity depending upon the
circumferential speed of the pulley 12. It will be noted that the
constant feeder section 10 may be alternatively of any other
conventional form. The feeder section 10 serves to determine the
average feeding velocity of the wire member 2 and in addition to
have no effect on the supply source 3 from periodical variation in
tension exerted on the wire member 2 upon pulsatory movement
thereof by means of the modulator section 11 which will be
described herein-just below.
The modulator section 11 may preferably comprise a metallic guide
pulley 28 having a shaft 29 secured thereto and journalled on a
bracket 30 by any conventional means, which may be secured to the
frame assembly 9 as by means of welding, and a metallic oscillating
pulley 31 which will be described herein-just below. The
oscillating pulley 31 may be rotatably supported on a reciprocating
rod 32 at one of the ends thereof, which moves while guided by a
guide assembly 33 which may be in turn mounted on the frame
assembly 9 as described hereinafter. The wire member 2 from the
feeder section 10 passes around the guide pulley 28 at half portion
thereof and then around the oscillating pulley 31 at half portion
thereof in the direction indicated by an arrow of FIG. 10, after
which it is fed into the extruder 5 shown in FIG. 1.
The guide assembly 33, which is illustrated in FIG. 13 in more
detail, may comprise a housing 34 in which the reciprocating rod 32
is disposed and slidably extends through a bushing 35 mounted on
and extending through the housing wall. The reciprocating rod 32 at
the other end thereof has an inner sleeve 36 fitted and secured
thereto by a screw 37. The rod 32 may be provided adjacent to the
other end thereof and on the outer periphery thereof with a key 38
received in a longitudinal key way 39 in the inner periphery of the
sleeve 36 to assure to prevent the rod from rotating relative to
the sleeve. Around and on the inner sleeve 32 is disposed an outer
sleeve 40 which in turn slidably engages the housing 34 at the
inner surface thereof. The outer sleeve 40 may have a shoulder 40a
engaging a corresponding shoulder 36a provided on the inner sleeve
36. A key 41, which is provided on the outer periphery of the
sleeve 40, is received in a longitudinal key way 42 provided in the
inner periphery of the housing 34 to assure to prevent the outer
sleeve 40 from rotating relative to the housing. The inner and
outer sleeves 36 and 40 may be preferably secured to one another as
by welding. Around the inner sleeve 36 is disposed a coil spring
43, one end of which engages a shoulder 35a integral with the
bushing 35 and the other end of which engages the shoulder 40a of
the outer sleeve 40, so that the inner and outer sleeves 36 and 40
together with the reciprocating rod 32 are urged in a leftward
direction as viewed in FIG. 13.
In order to effect the reciprocation of the oscillating pulley 31
along the longitudinal axis of the rod 32, there is provided with
cam means comprising cam 44 removably mounted on a cam shaft 45
which is in turn supported by a pair of bearings 46 and 46' at the
top of the frame assembly 9 (see FIG. 12) and a cam follower 47
pressed against the cam 44. The cam follower 47 may be preferably
in the form of a bearing race rotatably mounted on a shaft 27a as
shown in FIG. 13, which is in turn securedly mounted on an
extension 36b of the inner sleeve 36 extending from the housing 34.
Thus, rotation of the cam 44 about the axis of the cam shaft 45
causes the cam follower 47 to reciprocatively move on the periphery
of the cam 44 along the longitudinal axis of the rod 32 with the
result that the oscillating pulley 31 accordingly moves so that the
feeding velocity of the wire member 2 is modulated. It will be
appreciated that the profile of the cam 44 determines the wave
form, maximum and minimum values of the feeding velocity of the
wire member 2 while the r.p.m. of the cam 44 determines the
variation pitch or cycle of the feeding velocity. Therefore, it
will be understood that the velocity characteristic as desired can
be accomplished by properly replacing the cam 44 for another
specific one.
Referring again to FIGS. 10 and 11, a second reduction gear 48 is
mounted on the base of the frame assembly 9 and includes on one of
the sides thereof an input shaft 49 having a pulley 50 secured
thereto and on the other side an output shaft 51 having a pulley 52
secured thereto. An endless belt 53 engagingly passes between the
pulley 22 on the first reduction gear 20 at the other groove 22b
thereof and the pulley 50 on the second reduction gear 48 so that
the input shaft 49 of the reduction gear 48 is driven by the motor
18 through the pulley 22 on the first reduction gear 20. A third
reduction gear 54 is mounted on the base 9a of the frame assembly 9
and includes on one of the sides thereof an input shaft 55 having a
pulley 56 secured thereto and on the other side an output shaft 57
having a pulley 58 secured thereto. An endless belt 157 engagingly
passes between the pulleys 52 and 56 so that the third reduction
gear 54 is driven by the second reduction gear 48.
Referring again to FIG. 12, on the top of the frame assembly 9 is
provided a fourth reduction gear 59 including an input shaft 60 in
a common vertical plane to the output pulley 58 with a pulley 61
secured to the shaft 60 and opposite the input shaft an output
shaft 62 having a pulley 63 secured thereto. An endless belt 64
engagingly passes between the output pulley 58 on the third
reduction gear 54 and the input pulley 61 on the fourth reduction
gear 59 so that the fourth reduction gear 59 is driven by the
output of the third reduction gear 54. On the cam shaft 45 of cam
means is securedly mounted on a common plane to the output pulley
63 on the fourth reduction gear 59 a pulley 164 which has an
endless belt 65 on one of the sides thereof engaging therewith and
the belt 65 on the other side engages with the pulley 63 on the
fourth reduction gear so that the cam 44 can be driven by the
fourth reduction gear 59.
It should be noted that a plurality of reduction gears 20, 48, 54
and 59 aid in ranging wide variable ratios of speed of the cam 44
and therefore, making variation pitch or cycle of feeding the wire
member 2 variable in multiple steps.
Referring now to FIG. 14, there is shown a schematic diagram of the
extruding system in accordance with the present invention wherein
another embodiment of pulsatingly feeding means is provided to be
suitable for practising the present method, and in which the same
reference numerals designate the same components as those of FIGS.
1, 10 and 11. The wire member 2 passes through the constant feeder
10 as shown in FIGS. 10 and 11 and then through a shock absorber 66
into an electric velocity modulator 67 which will be described
hereinbelow. The covered wire member 2', after leaving the
modulator 67 may pass through another shock absorber 66'. The shock
absorbers 66 and 66' may each in the form of a conventional
accumulator comprising a plurality of guide rolls 68 and 68' and a
dancer roll 69, around which the wire member 2 and the covered
member 2' engagingly pass, as shown in this figure. The electric
velocity modulator 67 comprises capstans 70 and 70' disposed on the
input and output sides of the extruder 5, respectively, for
frictional engagement of the wire member 2 and 2' therewith and low
inertia motors 71 and 71' to drive the respective capstans 70 and
70'. Frictional engagements of the wire member 2 with the capstan
70 and of the covered wire member 2' with the capstan 70' are
effected by winding the members 2 and 2' around the respective
capstans and as a result the members run responsive to revolutions
of the capstans. The covered wire member 2' may be preferably wound
around the capstan 70' after its solidifcation through the cooling
trough 7. The low inertia motors 71 and 71' may comprise those
commercially available under trademark "MINERTIA MOTOR" and
manufactured by The Yasukawa Electric Co., Ltd. of
Fukuoka-Prefecture, Japan, which is a D.C. motor the speed of which
is controlled by an applied voltage. The low inertia motors 71 and
71' are so controlled by a common oscillator 72 that both motors
are synchronized in their speeds. More particularly, signal from
the oscillator 72 is amplified by amplifiers 73 and 73' to apply it
to respective controlled rectifiers 173 and 173', such as
thyristors for example to control the D.C. voltages applied across
the motors 71 and 71'. The amplitude, wave form and cycle of the
D.C. voltages across the motors 71 and 71' may be determined as
desired by output wave form from the oscillator 72. One of the
features of the embodiment shown in FIG. 14 is that because of
modulating means disposed on both the input and output sides of the
extruder 5 the wire members 2 and 2' are more precisely fed in
accordance with this embodiment than in cases wherein the modulator
11 is disposed only on the input side of the extruder, with the
result that portion of the wire member between the input and output
sides of the extruder has no variation in tension.
Referring now to FIGS. 15 to 23, there are illustrated some
extruder dies in their outlet profiles suitable for practice of the
method in accordance with the present invention. Considering
application of an extruded covering on an elongated core member
according to the present invention in view of rheology, while the
core member has been fed through the extruder at predetermined and
constant forward velocity in a conventional manner, flow of
thermoplastic material at the outlet of the die has a
characteristic wherein drag and pressure flows of thermoplastic
material are included, because thermoplastic material is dragged
with material attached to the core member, but either during
decelerating forward movement of the core member, during reversely
moving the same or during stopping movement of the same, flow of
thermoplastic material presents a characteristic wherein only
pressure flow is included. The covering extruded on the core member
with drag flow of thermoplastic material has no trouble since no
variation occurs in the outer diameter and also in appearance of
the covering. However, the covering extruded with pressure flow of
thermoplastic material has variation in appearance due to various
distal effects applied on material within the die. The distal
effects generally include melt fracture and Barus effects. The
former is that appearance of the covering on the core member
becomes irregular due to variation in flow of thermoplastic
material caused by shear stress from the extruder die wall and the
latter is that irregular appearance occurs in the covering because
during passage of material through the flow path therefor it tends
to be subject to various shear strain which is accumulated as inner
energy and then restored or relieved at the die outlet to expand
material to be attached to the core member. The covering and more
particularly the outward extensions thereof, subject to such distal
effects, result to be considerably deformed in appearance to
provide no desired configuration to the covering. This tendency
increases as shear rate becomes larger and as a result considerable
variation occurs in appearance of the covering. The inventors have
discovered that provision of desiredly shaped recess in the
extruder die at the front thereof cause the appearance of the
covering extruded on the core member with pressure flow of material
to be regulated by the configuration of the die outlet, as
desired.
Referring now to FIG. 15, there are shown in vertical section an
extruder die 74 and a nipple 75 disposed in the die in a coaxial
relation thereto, and melted thermoplastic material 76 is fed
through a cross head (not shown) by a feeding screw within a barrel
(not shown) of the extruder into a passage way 77 defined by the
die 74 and the nipple 75 while the wire member 2 passes through a
longitudinal bore 75a in the nipple 75 and then through an
extruding passage way 77a at the varied velocity by pulsatingly
feeding means as afore-mentioned, to thereby attach the covering 6
onto the wire member 2. As already described, normal extruding
condition in which the thinner portions 6b of the covering 6 are
being formed on the core member is based on flow of material
including drag flow, causing no variation in their cross section,
but the thicker portions 6a of the covering 6 are generally based
on pressure flow of material 76, tending to produce variation in
the cross section thereof. A circular recess 74a provided in the
die outlet at the front thereof controls variation in the cross
section of the covering thicker portions 6a and particularly
variation in the surface profile L of the thicker portions 6a
facing the supply source or on the leftward side as viewed in FIG.
15. The surface profile R of the thicker portions 6a facing the
coiler or on the rightward side of this figure will be determined
by the feeding velocity of the wire member 2 on which the covering
6 is applied.
FIGS. 16A and 16B show the outlet recess 74a in the extruder die 74
in an enlarged manner, which is made to conform to the
configuration of the covering thicker portions to be extruded as
desired. Thus, the base or bottom face of the outlet recess 74a
shown in FIGS. 16A and 16B is seen to be of three dimensional or
hemispheric face conforming to the surface profile L of the thicker
portions 6a as shown in FIGS. 17A and 17B. The die outlet recess
74a shown in FIG. 16A has a length or depth dependable upon the
thickness D and space or pitch P of the desired covering thicker
portions 6a and the corelation between them is defined by the
formula, D<T<P.
A die 78 shown in FIG. 18 has an outlet recess 78a adapted to
extrude a covering 80 having a disk-like insulation 80a of
thermoplastic resin, on an elongated center or inner conductor 79
of an electric coaxial cable, for example as shown in FIG. 19. It
will be understood that since enlarged portions of the covering are
disk-shaped the outlet recess has a bottom face of two dimensional
circle.
An extruder die 81 shown in FIG. 20 has an outlet recess 81a the
bottom face of which is generally of circular cone. Such die is
adapted to make on a wire member 82 an extruded covering 83
including an enlarged portions 83a of a particular profile as shown
in FIG. 21. The covering 83 shown in FIG. 21 is also adapted to be
used as an insulator of a coaxial cable in the same manner as
described in connection with the afore-mentioned embodiments.
Referring now to FIG. 22, an extruder die 84 has a die body 85 with
a front or outlet portion 86 including an outlet recess 86a similar
to that of the embodiment afore-said in connection with FIGS. 15
and 16, separated and thermally insulated from the die body 85 by
means of thermal insulator, such as mica plates 87 inserted between
the die body 85 and the front portion 86 and secured thereto by any
suitable means, so that high temperature from the extruder is
prevented from being transported to the front portion 86 of the die
81. After melted material has been attached to the core member and
then molded conforming to recess 86a in the die outlet because of
the core member reduced in feeding velocity, stopping or moved in
backward direction, the covering of melted material on the core
member can be easily relieved from the recess wall of the die
outlet. In the illustrated embodiment, the front portion 86 of the
extruder die is found to be provided with a path 88 extending
therethrough and through which a cooling water is recirculated for
promotion of cooling the front portion 86. An extruder die 89 shown
in FIGS. 23A and 23B has a die body 90 with a front or outlet
portion 91 including a recess 91a similar to that of FIG. 22,
separated and thermally insulated from the die body 90 by means of
a thermal insulator 92 in the same manner as described in
connection with the extruder die 84 of FIG. 22, but the front
portion 91 is provided with a plurality of radial fins 91b by which
the cooling water path 88 of FIG. 22 is replaced, for cooling the
front portion 91. It will be understood that the covering molded by
the recess 91a can be easily relieved from the recess wall in the
same manner as afore-described. Although the extruder dice 84 and
89 of FIGS. 22, 23A and 23B are shown to have the substantial same
profile as that of FIGS. 16A and 16B, it will be understood that
they may have any other profiles.
Referring now to FIGS. 24 and 25, an electric coaxial cable is
generally indicated by numeral 93 and comprises a wire-like center
or inner conductor 94 which may be formed of aluminium or copper
and a tubular outer conductor 95 coaxially disposed around the
inner conductor and which may be also formed of aluminium or
copper. On the inner conductor 94 is mounted an insulation 96
adapted to insulate the inner conductor 94 from the outer conductor
95 and also to position them in a coaxial relation to each other.
The insulation 96 may be formed by being extruded on the inner
conductor 94 as a core member in the same manner as described in
the aforesaid embodiments. It should be noted that the coaxial
cable 93 has the insulation 96 applied on the inner conductor 95
overall the entire length thereof, which is essentially different
from a conventional type of coaxial cable having a disk-like
insulator between the inner and outer conductors, and therefore
deformation of the outer conductor 95 will not cause it to
electrically contact with the inner conductor 94. The insulation 96
has a plurality of spaced and alternate thinner portions 96b formed
during higher velocity of the inner conductor 94 through the
extruder and a plurality of alternate thicker portions 96a formed
during negative velocity of the inner conductor 94 through the
extruder. Such insulated inner conductor, referred to hereinafter
as an insulated core, is desired to be formed so that the portions
96b of the insulation 96 may be as thinner as possible and that the
disk portions 96a may have a steep contour and be sufficiently
larger in the diameter than that of the inner conductor 94.
Accordingly, the inner conductor may be preferably fed through the
extruder in accordance with the characteristic in which
intermittent backward movements of the conductor are included as
shown in FIG. 6 and 8. Among others, the characteristic shown in
FIG. 8 is suitable for manufacture of the insulated core for the
coaxial cable.
The disk portions 96a of the insulation 96, having a plane
substantially perpendicular to the axis of the inner conductor 94
and an outer diameter substantially equal to the inner diameter of
the outer conductor 95, have the maximum thickness t.sub.1 enough
to maintain their mechanical and electrical strengths. The thinner
portions 96b of the insulation 96, which are necessary only for
prevention of short-circuiting the inner and outer conductors, have
the thickness t.sub.2 considerably smaller than the thickness
t.sub.1 of the portions 96a. Preferably, the ratio of the thickness
t.sub.2 relative to the thickness t.sub.1 may range between 1/2 and
1/20. Thus, the thinner portions 96b of the insulation
advantageously improves the flexibility of the coaxial cable 93 and
facilitates removal of the insulator 96, whicch will be required
when the coaxial cables are intended to be connected to each
other.
Referring to FIG. 26, there is schematically shown a system
suitable for forming an outer conductor for the co-axial cable 93
shown in FIG. 24, wherein the insulated core 196 including the
insulation 96 applied on the inner conductor 94 as described
hereinabove is fed in the direction indicated by an arrow, along
which strip or tape 97 of either copper or aluminium from a supply
98 is fed through a guide roll 99 into a forming apparatus (not
shown) in which the strip 97 is rolled up around the insulated core
196 into a cylindrical body 97', the abutting edges 97a of which
may be welded as by a TIG welding torch 100 or the like. It should
be noted that the cylindrical body 97' has somewhat larger inner
diameter than the outer diameter of the disk portions 96a of the
insulation 96 so that both can be spaced from each other.
Thereafter, the cylindrical body 97' is reduced in diameter through
a shrinking device 101, such as a drawing die, for example to be
thereby jointed to the disk edges of the insulation 96. Preferably,
a heater assembly (not shown), which may be of any conventional
form, may be provided in the shrinking device for heating the
cylindrical body 97' during its reduction in diameter to thermally
bond the inner periphery of the body to the edges of the disk
portions 96a. This advantageously prevents water entering the cable
through the pinhole, etc. in the outer conductor from running
longitudinally between the insulation 96 and the outer conductor
95. In order to improve thermally bonding of the outer conductor 95
to the disk portions 96a, it is desirable to use ethylenic
copolymer as thermoplastic material of which the insulation 96 is
formed.
Referring then to FIG. 27, there is shown in front view a modified
extruder die 102 which is provided with longitudinal grooves 103 in
the opening wall 104 of the die 102 on opposite sides thereof. FIG.
28 shows an electric wire 105 comprising core conductor on which
thermoplastic material is extruded while the core conductor is fed
through the extruder die 102 at pulsatingly varied velocity of the
core conductor as described in the afore-mentioned embodiments. The
electric wire 105 is seen to have a covering layer 106 on the
conductor core 107, including opposing longitudinal ribs 108 formed
by the grooves 103 in the die 102 and longitudinally spaced and
peripheral ribs 109 formed by feeding the core conductor through
the die 102 at pulsatingly varied velocity of the core conductor.
With such electric wire installed, when it would have highly humid
and weighty snow gathering on it, the longitudinal and peripheral
ribs 108 and 109 prevent snow on the cable from moving
longitudinally and peripherally and therefore, growing into a
larger lump. Therefore, the electric wire will be prevented from
its breakage due to collection of snow on it.
While preferred embodiments of the present invention have been
described with reference to the accompanying drawings, it would be
apparent to those skilled in the art that various changes and
modifications might be made from the teachings of the disclosure in
the specification without departing from the present invention. By
way of examples, the modulator may be of other equivalents
electrically or mechanically operated and the arrangement shown in
FIG. 14 can be applied on a mechanically variable feeder.
Therefore, such modifications will apparently fall within the
spirit and scope of the present invention, which is not intended to
be limited to the embodiments, except by the appended claims.
* * * * *